Petroleum crude oils often contain variable amounts of water that are emulsified within the oil. These emulsions can be very stable and difficult to disrupt. As such, such emulsions present problem to further processing of crude oils. Oil-external water-internal emulsions are sometimes rejected because of their excessive water content. Thus, the producing company must address the issue of water-in-oil emulsions in order to sell the crude oil they produce.
In the first half of the 20th century, calcium hydroxide hydrolyzed fats and sulfonated oils were used to break oil-external water-internal emulsions. With the advent of epoxides (e.g., ethylene oxide, propylene oxide, and butylene oxide) in the 1940's, new products, such as oxyalkylated alcohols and amines, were produced which were shown to have high specific activity for the breaking of such emulsions. Since around 1945 to the present day, enormous arrays of products that employ epoxides have been produced which vary in effectiveness from no activity (failing to break the emulsion) to highly active (capable of breaking the emulsion immediately). In the late 1950's, it was determined that the molecular weight of such epoxides was key to their effectiveness to completely resolve emulsions. Since that time, attempts have been made to increase the molecular weight of such demulsifying agents.
One of the more successful means of increasing the molecular weight was seen with bis-phenol-diepoxide adducts of the oxyalkylated derivatives or the virtual molecular weight doubling of the derivative. Additional attempts that met with partial success included the use of diisocyanates as well as dicarboxylic acids as molecular weight extension agents. Further, some unsuccessful attempts were made to oxyalkylate polyvinyl alcohol. Efforts continue today to develop a composition capable of demulsifying crude oil emulsions.